Swiss cheese sign (lungs)
The Swiss cheese sign has been used for the appearance on CT of fluid-containing pneumatoceles, that typically occur following pulmonary lacerations . They have also been described on CT appearances where there is pulmonary infection superimposed on emphysema .
The pneumatocoeles appear as 'holes' in the lung parenchyma and hence the description with respect to Swiss-style cheeses (e.g. Emmental), which contain multiple holes.
Other usage
It is sometimes used by pathologists to describe the gross pathological appearance in juvenile papillomatosis of the breast.